Use of 2,6 - di-tert-butyl-4-methylphenyl n - dichloroacetyl-n-methylcarbamate as a herbicide

ABSTRACT

DISCLOSED IS THE USE OF 2,6-DI-T-BUTYL-4-METHYLPHENYL N-DICHLOROACETYL-N-METHYLCARBAMATE AS A PREEMERGENCE HERBICIDE FOR ANNUAL WEEDY GRASSES IN RICE FIELDS.

United States Patent Ofiice USE OF 2,6 DI-TERT-BUTYL- l-METHYLPHENYL NDICHLOROACETYL-N-METHYLCARB'AMATE AS A HERBICIDE Albert H. Haubein,Newark, Del., assignor to Hercules Incorporated, Wilmington, Del.

No Drawing. Original application Apr. 19, 1968, Ser. No. 722,553, nowPatent No. 3,531,515. Divided and this application June 3, 1970, Ser.No. 54,028

Int. Cl. A01n 9/24 U.S. Cl. 71-106 Claims ABSTRACT OF THE DISCLOSUREDisclosed is the use of 2,6-di-t-butyl-4-methylphenylN-dichloroacetyl-N-methylcarbamate as a preemergence herbicide forannual weedy grasses in rice fields.

The application is a division of the US. patent application, Ser. No.722,553, filed Apr. 9, 1968, on which US. Pat. 3,531,515 was granted.

This invention relates to a new compound. More particularly, it relatesto 2,6-di-t-butyl-4-methy1phenyl N-dichloroacetyl-N-methylcarbamate andits use as a herbicide.

It has been found in accordance with the present invention that2,6-di-t-butyl-4-methylphenyl-N-dichloroacetyl-N-methylcarbamate, whichhas the structural formula is a new compound which is tolerated by allstages of growth of certain desirable crops such as corn, cotton, barleyand rice, but which acts effectively as a preemergence herbicide to killseedlings of annual weedy grasses.

Annular weedy grasses represent undesired vegetation in fields of cropssuch as those just mentioned. Except in the case of rice, these grassescan be controlled by post-emergence treatment with known herbicideswhich are not phytotoxic to the crop plants at the dosages required forcontrol of the grasses. However, rice is very sensitive to the action ofmost herbicides used for grass control, and there are very few productsavailable which are acceptable.

Probably the most widely used rice herbicide is the compound3,4-dichloropropionanilide. This compound is applied as a post-emergenceherbicide, usually at a rate of about three to about five pounds of theactive compound per acre for the control of grasses and many broadleavedweeds. The major disadvantage of this compound is that it has little orno residual activity. As a consequence, if additional weeds germinateafter application of the compound, there still may be a weed controlproblem facing the applicator. In contrast, the compound of thisinvention is characterized by its pre-emergence activity against annualweedy grasses and by exhibiting a desirable residual activity. Thecompound of this invention also differs from the compound from which itis prepared, namely 2,6-di-t-butyl-4-methylphenyl N-methylcarbamate. Thelatter compound also will effect preemergence control of annular weedygrasses, but it is phytotoxic to rice and therefore cannot be used inthat application.

3,702,760 Patented Nov. 14, 1972 The 2,6-di-t-butyl-4-methylphenylN-dichloroacetyl-N- methylcarbamate may be prepared by efiectingreaction between a metal salt of 2,6-di-t-butyl-4-methylphenylN-methylcarbamate and dichloroacetyl chloride( Stefanye et al., J. Am.Chem. Soc., vol. 77 (1955), pages 3663-4). It also may be prepared bythe reaction of 2,6-di-t-butyl- 4-methylphenyl chlorocarbonate withN-methyl dichloroacetamide. The preferred method, however, comprisingheating 2,6-di-t-butyl-4-methylphenyl N-methylcarbamate withdichloroacetyl chloride, in which reaction hydrogen chloride is evolved.An inert solvent of suitable boiling range, such as toluene or xylene,may be utilized, if desired. The temperature of this reaction should besufiiciently high to cause hydrogen chloride formation, but not so highas to cause product decomposition. A preferred reaction temperaturerange is from about C to about 140 C.

The preparation of 2,6-di-t-butyl-4-methylphenylN-dichloroacetyl-N-methylcarbamate and of herbicidal compositionscontaining it, and evaluation of the herbicidal compositions are setforth in the following examples. In the examples, all parts andpercentages are by weight unless otherwise specified.

EXAMPLE 1 A mixture of 2,010 parts of 2,6-di-t-butyl-4-methylphenylN-methylcarbamate (prepared from 2,6-di-t-butyl- 4-methylphenol andmethylisocyanate) and 2,100 pants of dichloroacetyl chloride was heatedat C. for 30 hours while slowly sparging with nitrogen. Upon completionof the reaction, as indicated by essential absence of hydrogen chloridein the off-gas, the reaction mixture was cooled. This resulted in theformation of crystals which were separated from the rest of the reactionmixture by filtration and then washed with hexane. The filter cake wasrecrystallized from Phillips solvent, a petroleum distillate boiling atabout C., to give 2,897 parts of white crystals having a melting pointof 153-155 C. The crystals analyzed for 18.1% chlorine, the theoreticalamount for the carbamate product being 18.2%. Infrared and nuclearmagnetic resonance spectra were consistent with the structure of2,6-dil-t-butyl-4-methylphenyl N-dichloroacetyl-N-methylcarbamate.

EXAMPLE 2 The compound of this invention was subjected to a screeningtest for evaluating pre-emergence herbicidal activity. To do this therewas prepared an aqueous suspension containing 15 grams of the compoundper liter and spraying twice at the rate of 80 gallons per acre for atwenty-pound-per-acre test on soil containing seeds which had beenplanted 24 hours earlier. The aqueous suspension was made by dissolvingthe compound in acetone to a concentration of 15 grams per 200 m1.acetone solution, adding Tween 20 (a sorbitol monolauratepolyoxyethylene derivative) to a concentration of 10 grams per 200 ml.of the acetone solution, and diluting the acetone solution with water tobring the concentration to 15 grams of the compound per liter.

The seeds used in the screening test were millet (Setaria sp.), corn,(Zea mays L.), mustard (Brassica juncea Cross. var. crispifolia), andcotton (Gossypium hirsutum). After treatment the seeds were allowed togerminate and grow for a period of three weeks, and during this time theminimum temperatures were approximately 70 F. During the three-weekperiod the seeds and seedlings were watered, the first two wateringsbeing done by sprinkling in order to leach the compound into the soil.Thereafter, water was applied by subirrigation. Data were taken threeweeks after treatment. The numerical values given in the following tableare based on a 0-10 rating scale in which means no damage to the plantsand indicates complete kill of the plants.

TABLE I Species Mil- Mus- Cot- Compound Rate let Corn tard ton2,6-dl-t-butylA-methylphenyl 20 lbs./ 8+ 2 5 0N-dlchloroacetyl-N-methylcaracre.

bamate.

EXAMPLE 3 The procedure followed in Example 2 was repeated for2,6-di-t-butyl-4 methylphenyl N-dichloroacetyl-N- methylcarbamate in asecondary test for evaluation of herbicidal activity using a total ofdifferent plant species. The procedure of Example 2 also was varied tothe extent of using rates of application which were 2, 4 and 8 poundsper acre, respectively. The formulation for the two-pounds-per-acreapplication was prepared by taking 100 ml. of the original formulation,diluting this to 1,000 ml. with a mixture composed of acetone, 1% Tween20 and 79% water, and spraying twice with the resulting formulation atthe rate of 80 gallons per acre. Similar formulations for thefourpounds-per-acre and eight-pounds-per-acre applications were preparedin the same manner except to use 200 ml. and 400 ml., respectively, ofthe original formulation. These formulations also were sprayed twice atthe rate of 80 gallons per acre. After treatment the seeds were allowedto germinate and grow for three weeks. Ratings on the elfect of thecompound of this invention were made three weeks after treatment, as inExample 2. The seeds used in this test were as follows:

Millet (Setaria sp.)

Cotton (Goasypium hirsutum) Crabgrass (Digitaria sp.)

Wild Oats (Avena fatuw) Wheat (Triticum aestiyum L.)

Barley (Hordeum valgare L.)

'Soy bean (Soja Max.)

Sudan grass (Sorghum valgare var. sudanese) Rice (Oryza swtiva L.)

Sorghum (Sorghum valgare var. durra) Ryegrass (Loliumi pefenue L.)

Downy brome (Bro'mus tectorum L.) Penncross bentgrass (Agroatispalustrus H uds.) Red top (Agrostis alba L.)

Fine fescue (Festuca ovina L.)

EXAMPLE 4 The 2,6-di-t-butyl-4-methylphenyl N-dichloroacetyl-N-methylcarbamate next was evaluated in small scale field tests. The plotsutilized had previously been heavily seeded with barnyard grass andsignal grass (Brachiaria). In the month of May the plots were plantedwith rice seed, variety Bluebell, using the drilling technique, Theplots were cultipacked and 2,6-di-t-butyl-4-methylphenylN-dichloroacetyl-N-methylcarbamate, formulated as a 4 50% wettablepowder, was applied at rates of 2, 3, 4,

6 and 8 pounds of the carbamate per acre. After application of thecarbamate formulations, the plots were lightly irrigated. The riceplants emerged 10 days later. Because almost five inches of rain hadfallen two days after the rice was planted, no additional irrigation wasrequired. Twenty-seven days after planting the rice, there was someevidence of stand reduction in the crop on those plots treated at therate of 8 pounds of the carbamate per acre. No such reduction wasevident for those plots treated at the other rates of application. Grasscontrol was satisfactory at the rates of four, six and eight pounds ofthe carbamate per acre.

The 2,6-di-t-butyl-4-methylphenyl N-dichloroacetyl-N- methylcarbamate ina herbicidal amount is applied according to any of the methods suitablefor herbicide application, for example, as solvent solutions or incombination with solid or liquid extenders or adjuvants. Suitablesolvents for the preparation of solvent solutions, which may either beused directly or after dispersion in an immiscible liquid or on a solidcarrier, include pine oil, alcohols, hydrocarbon solvents such asxylene, methylated naphthalene, and isophorone, difluorodichloromethane,deodorized kerosene, cyclohexanone, methyl isobutyl ketone, and othersimilar organic solvents. When such a solvent solution is to be useddirectly, the concentration of the carbamate contained therein may rangefrom about 10% to about based on the weight of the soltuion. Otherwise,the carbamate concentration in solution will be adjusted so that uponfurther dilution the desired ultimate concentration results. Amounts ofthe carbamate ranging from about 0.1% to about 10% by weight of thediluted formulation have generally been found to be suitable.

In many instances it will be most advantageous, for reasons of economy,facility of application, etc., to employ the carbamate in admixture withsolid or non-solvent liquid extenders. Such extenders include water andsolid carrier materials, preferably those that are readily available andinexpensive, such as talc, attapulgite, natural clays, pyrophylite,diatomaceous earth, kaolin, aluminum and magnesium silicates,montmorillonite, and similar substances such as are used as carriers inthe insecticide and herbicide arts. Using such solid materials asextenders, wettable powders and dusts may be formulated. In manyinstances, the extenders envisioned for use in this invention willthemselves possess surface-active properties, in which case they mayproperly be termed dispersants. In other instances, such as when wateris used, the extender possesses no surface-active properties of its own,and an additional material will be added to aid in the dispersion of thecarbamate throughout the extender. It should be realized that while itis generally advantageous to distribute as uniformly as possible thecarbamate over surfaces to which the herbicide is applied, through theuse of surface-active agents when necessary, there may be circumstancesunder which it is desired to omit such agents; such cases are alsointended to be within the scope of this invention. The carbamateconcentrations in these extended formulations may vary within widelimits; suitable concentrations for application in the field range fromabout 0.01% to about 20% of the carbamate based on the total weight offormulation.

The aqueous dispersions contemplated herein comprise the carbamate ofthis invention, water and a surfaceactive dispersing agent. Ordinarilyan aqueous dispersion will be made up from a concentrate comprised ofthe carbamate compound and a surface-active agent, which concentratewill subsequently be dispersed in water to a desired concentration. Theamount of the carbamate compound contained in a spray properly dilutedfor application in the field will generally range from about 0.01% toabout 20% of such an aqueous dispersion. In most instances, the amountof surface-active agent used will be from about 1% to about 25% of theamount of the carbamate present. Organic solvents may also be containedin the concentrate to aid in effective dispersion.

Suitable surface-active dispersing agents for use in the compositions ofthis invention are those disclosed in Chemistry of Insecticides,Fungicides, and Herbicides, (Donald E. H. Frear, second edition (1948),pages 280- 287) for use with known insecticides. They include neutralsoaps of resin, alginic, and fatty acids, with alkali metals,alkyl-amines or ammonia; 'saponins, gelatins, milk, soluble casein,flour and soluble proteins thereof, sulfite lye, lignin pitch, sulfiteliquor, long-chain fatty alcohols having 12-18 carbon atoms and alkalimetal salts of the sulfates thereof, salts of sulfated fatty acids,salts of su1- fonic acids, esters of long-chain fatty acids andpolyhydric alcohols in which alcohol groups are free, solid dispersantssuch as fullers earth, China clay, kaolin, attapulgite, and bentoniteand related hydrated aluminum silicates having the property of forming acolloidal gel. Among the other surface-active dispersing agents whichare useful in the compositions of this invention are theomega-substituted polyethylene glycols of relatively long chain length,particularly those in which the omega substituent is aryl, alkyl, oracyl.

Compositions of the carbamate and surface-active dispersing agent willin some instances have more than one surface-active dispersing agent fora particular type of utility. For example, the carbamate may containsurfaceactive clay as the sole adjuvant or clay and anothersurface-active dispersing agent to augment the dispersing action of theclay. Similarly, as is hereinbefore described, the carbamate mayhavewater admixed therewith along with a surface-active dispersingagent, most often the amount of water added being sulficient to form anemulsion. All of these compositions comprising the carbamate andsurface-active dispersing agents may contain, in addition, synergistsand/or adhesive or sticking agents. Moreover, the recital of specificclasses of additives is not intended to limit the scope of thisinvention thereto, but it is to be understood that the addition of othermaterials to these formulations is also envisioned.

What I claim and desire to protect by Letters Patent is:

1. A herbicidal composition comprising a herbicidal amount of2,6-di-t-butyl-4-methylphenyl N dichloroacetyl-N-methylcarbamate inadmixture with a surfaceactive dispersant.

2. A herbicidal composition comprising a herbicidal amount of2,6-di-t-butyl-4-methylphenyl N dichloroacetyl-N-methylcarbamate insolution in a solvent therefor.

3. A herbicidal composition comprising a herbicidal amount of2,6di-t-butyl-4-methylphenyl N- dichloroacetyl-N-methylcarbamatedispersed in a major amount of water.

4. A herbicidal composition comprising a herbicidal amount of2,6-di-t-butyl-4-methylpheny1 N dichloroacetyl-N-methylcarbamate inadmixture with a major amount of a solid carrier material.

5. The method of controlling grass vegetation in a rice field, whichcomprises contacting the soil in said field, prior to emergences of saidvegetation, with a herbicidal amount of 2,6-di-t-butyl-4-methylphenyl Ndichloroacetyl-N-methylcarbamate.

References Cited UNITED STATES PATENTS 3,140,167 7/1964 Haubein 71-1063,337,600 8/1967 Speziale et a1 71--106 X 3,592,949 7/1971 Teach et a1.71106 X JAMES 0. THOMAS, 111., Primary Examiner

